DEVELOPMENT OF RESTING SPORES ON PLANTS INOCULATED WITH A DIKARYOTIC RESTING SPORE OF PLASMODIOPHORA-BRASSICAE

A dikaryotic resting spore or two monokaryotic resting spores of Plasm odiophora brassicae were inoculated onto 1-d-old seedlings of Brassica campestris. The relative DNA content of a nucleus in a dikaryotic res ting spore corresponded with that of a haploid nucleus in a monokaryot ic resting spore. Plasmodia and zoosporangia were observed within the galls in some root cortical cells approximately 2 mo after inoculation . Resting spores were also formed within the galls in some cortical ce lls, and root hair infection was observed. The frequency of resting sp ore formation in B. campestris seedlings inoculated with a dikaryotic resting spore or two monokaryotic resting spores was 26.2 and 3.6%, re spectively. The results indicate that the life-cycle of P. brassicae w as completed on plants infected with a dikaryotic resting spore or by two monokaryotic resting spores.